Dual vortex liquid spray nozzle



M y 5 K. D. MGMAHAN 2,551,276

DUAL VORTEX LIQUID SPRAY NOZZLE Filed Jan. 22, 1949 In ve ntor:

Kent on D.- McMahan 1 WWW/WM l-lis Attorne g.

Patented May 1, 1951 DUAL VORTEX LIQUID SPRAY NOZZLE Kenton D. McMahan,Schenectady, N. Y., assignor to General Electric Company, a. corporationof New York Application January 22, 1949, Serial No. 72,216

1 Claim. 1

This invention relates to liquid spray nozzles, particularly those ofthe vortex type having spin chambers from which a conical spray emergesthrough a discharge orifice. While not limited thereto, the invention isparticularly intended for spraying liquid fuels such as kerosene, asused for instance in the combustors of gas turbine powerplants.

When used in gas turbine combustors, it is usually desirable, andsometimes absolutely essential, that the fuel spray nozzle produce aspray pattern in the form of a hollow cone having a very nearly fixedvertex angle, referred to hereinafter as the cone angle. Because of thevery precise design required in a combustor for a gas turbinepowerplant, especially those used in aircraft powerplants where thedevice must operate effectively over an extreme range of atmosphericpressures, it is necessary that the cone angle remain fixed over theextremely wide range of fuel supply pressures and flow rates, in orderthat the combustor will produce clean combustion with a stable flame,and be not subject to blow-out or other erratic operatingcharacteristics. For instance, in the small 300 H. P. gas turbinepowerplant for which the present invention was developed, a nozzle isrequired which will deliver fuel with a constant spray angle over arange of pressure from 50 to 500 pounds per square inch, correspondingto flow rates of from to 30 gallons per hour, over a range of altitudesfrom sea level to 40,000 feet.

is supplied through conduit 3, and a secondary port to which liquidunder pressure is supplied through conduit 4. The nozzle assembly issupported by being threadedly received, or otherwise secured, in abushing 5 welded into an opening in the outer housing or casing 6 of thecombustor. Spaced from the outer casing 6 is an inner liner or end domehaving a wall I with a central aperture through which the end of thenozzle tip assembly projects slightly, as shown. It will readily beappreciated by those skilled in the art that air under pressure issupplied from a suitable compressor (not shown) through inlet 8a to theplenum chamber 8 defined between the outer casing 6 and the inner liner1, from whence this air fiows into the reaction space defined within theinner liner through suitable openings la. Further details of thecombustor assembly are shown in my copending application Serial No.705,866, filed October 26, 1946, now Patent Number 2,510,645, andassigned to the assignee of the present application. The details of thecombustor and the fluid supply passages in the nozzle are not materialto an understanding of the present invention, which relates specificallyThe object of the present invention is to provide a satisfactory nozzleof the type described which will produce very nearly a constant sprayangle under the extremely difiicult operating conditions encountered inmodern aircraft gas turbine powerplants.

Other objects and advantages will be apparent from the followingdescription taken in connection with the accompanying drawing in whichFig. l is a view in elevation of a nozzle arranged in accordance withthe invention, showing its relation to the combustor and fluid supplylines, Fig. 2 is an enlarged detail view of the nozzle tip assembly;Fig. 3 is an end view in elevation of a component of the nozzle tipassembly; and Fig, 4 is another partial sectional View illustrating adetail of the nozzle cooling shroud.

Referring now more particularly to Fig. 1, the nozzle assembly indicatedgenerally at l consists of a housing or body member 2 which issubstantially cylindrical and has at one end a primary inlet port towhich liquid under pressure to the detailed arrangement of the spinchambers, fluid discharge orifices, and nozzle tip cooling shroud, asdescribed more particularly hereinafter.

Referring now to Fig. 2', the forward end of the nozzle housing 2 isprovided with an end portion 2a defining a conical inner surface 22)against which the nozzle tip assembly is held. Within the bore of thehousing 2 is an inner member 9 having one or more longitudinal groovesH! which cooperate with housing 2 to form longitudinal passagessupplying fluid from the inlet conduit 4 to the annular space II definedbetween the end of member 9 and housing 2. The inner nozzle member 9 isprovided with a central bore 12, which communicates with inlet conduit3. The end portion 9a of the inner nozzle member 9 defines a bore 9b inwhich is received the secondary nozzle tip member l3. Member l3similarly has a central bore 14 threadedly receiving the primary nozzletip member [5.

The primary tip member l5 has a central bore l6 forming an inlet chambercommunicating with the bore I2 and with a plurality. of drilled holes I!communicating with an annular chamber l8 defined between the reduced endportion of member [5 and the bore [4 of the secondary nozzle tip member[3. The conical end portion [5a of the primary tip member is providedwith a plurality of grooves or slots [9 communicating at their outerends with the annular chamber l8 and discharging tangentially into theprimary spin chamber 20 defined between the end of member l5 and theadjacent portions of the secondary tip member l3. The arrangement of theslots I9 may be seen more clearly in Fig. 3, which isan end view, inelevation, of the primary tip member I5.

As noted above, the secondary tip member 13 is received in the recess91), being clamped between the end portion 9a anditheadjaoentconicalsurface 2b of the housing endportion 2a. Besides cooperating with theprimary'tip member l5 to form the annular supply chamber '18 and theprimary slots I9, tip member [3 has a central conical bore 2| forming:an axial'extension of the primary spin chamber 20, terminating at acylindrical portion 2|a which forms the primary discharge orifice. Theconical end surfaceof tip member l3 which engagesthe surface Zbisprovided with a plurality of slots 22 having outer end portionscommunicating with the-annular supply chamber H and dischargingtangentially into an annular secondary spin chamber 23, which as-maybeseen inFig. 2 is of somewhatconical configuration and terminates at anannular secondary discharge orifice 23a.

'It will be-obvious to'those skilled in the art that innumerablemechanical arrangements are possible for defining the primary spinchambei 20 and orifice 2Iaandthe secondary spin chamber 23 and itsrelated discharge orifice 23d, and I of course do not contemplate thatmy invention is limited to the precise mechanical details shown in thedrawing. The important factors in my invention are the following:

1. The primary discharge-nozzle 2! is located within'what isordinarily-the air core" of the secondary spin chamber 23.

2. The sharp discharge edge of the primary orifice Zla is either exactlyor very nearly so, in'the plane of the dischargeedge of the secondaryorifice 23a.

W'ithmy nozzle, the cone angles of both the sprays formed bythe'prirnary and secondary nozzles are independently adjustable byvarying the angle and size of slots 49 and 22 respectively, which is notpossible with conventional duplex typenozzles. Likewise, the fiow -ratesof the primary and secondary nozzles are independently adjustable overextremely wide ranges.

In designing-a nozzle in accordance with the invention, the spinchambers and discharge orifices may be calculated, in accordance withweilknown principles governing the operation of such nozzles, so thatthe primary discharge orifice 2Ia, operating by itself entirelyindependent of the secondary orifice 23a, produces a spray pattern inthe form of a hollow cone having a vertex angle of the desiredmagnituda'for instance 60. Similarly the secondary spin'chamber 23 andits associated annular orifice 23a is designed to produce the sameconeangle when operating by itself.

In operation, the respective primary and secondary spin chambers anddischarge orifices cooperate toproduce a single combined conical spraywhichihasbeen found to remain constant over' an extremely .wideoperating range. For instance; in starting thecombustor at low rates offuel flow, :liquid' fuel is suppliedthrough conduit'3 at. a pressure ofabout 50 pounds per square inch, that" ispthe minimum value required to'produce'the'necessary spray angle from the primary discharge orifice21a. For increasing flow rates, the fuel supply pressure to the primaryorifice is increased from the initial value of 50 pounds per square inchup to perhaps 400 pounds per square inch, or even higher, over whichrange the primary orifice acting alone will produce the desired constantspray angle. Then to obtain still larger flow :rates, liquid is suppliedthrough the inlet conduit 4 to the secondary spin chamber and annularorifice 23a. When the "supply pressure of this secondary fluid is belowa certain critical value, for instance 35 pounds per square inch, thevelocities in the secondary spin chamber 23 are-not sumciently high toproduce good atomization, therefore the particle size in'the spray fromthe secondary orifice will belargerthan-the optimum for good combustion.The merging of this poorly atomized spray with the finely divided sprayfrom the primary orifice may cause the cone angle of the combined spraytodecrease, perhaps 5 or so. However, as the supply pressure to thesecondary spin chamber increases, the velocities therein increase;and,-at-a pressure of about 40 pounds per square inch, good atomizationis obtained from the secondary orifice andthecombined sprayangle-returns exactly to the desired design value. It has been foundthat with theprimary orifice operating at its maximum value and thesupply pressure to the secondary orifice varying over a widerange,forinstance from 40 to .400 pounds per square inch, the cone angleof the combined spray produced by the twoorifices will remain withinperhaps plus or minus 2 per cent of the desired design angle. This ismost desirable in a gas turbine combuster of the type described inmyaforementioned copending application.

Tests of an improved nozzle in accordance with my-invention reveal thatwhen operating in a gas turbine combuster, there is a tendency forunburned or partly burned fuel particles to deposit and carbonize on theouter end surface -2 cof the nozzle. If this accumulation of carbonprogresses far enough, it tends to overhang the edge of the secondaryannular orifice 23a, thereby "decreasing the area of, or even pluggingup completely, the orifice'ZF-a and-seriously interfering with theoperation of the nozzle. This deposition and accumulation of carbon onthe end wall' Zc may-be prevented by the cooling and insulating airshroud 24. This consists of a stamped or spun sheet metal cup having acircumferential axially extending portion 24a adapted to engage thecylindrical outersurface of housing 2. A central orifice 25 is formed inthe shroud 24 coaxial with the fluid discharge orifices 2la, 23a. Thediameter of opening 25 is somewhat largerthan the diameter of the spraycone at that location in order that liquid particles from the spraypattern will not be trapped by the shroud, but so that, instead, thecooling air flow through the shroud (referred to hereinafter) will havean annular exit orifice defined between the edge of the orifice 25 andthe outer surface of the spray cone pattern.

As may be seen in Fig. 2, the shroud sidewall 24a terminates at alocation between the inner liner 1 and the outer combuster housing 6.Formed in; the outer surface of nozzle housing 2 are a plurality oflongitudinally extending grooves 26, which are closedby the shroud wallportion 244 as shown in Fig. 4 so as to form cooling channelscommunicating with the air supply;plenum chambert atone end and with theannular space defined between the shroud 24 and the adjacent end surface20 of the nozzle body. It will therefore be apparent that the pressuredifferential between the plenum chamber 8 and the combustion space,which difi'erential causes the flow of combustion air into the reactionspace, will also cause a flow of cooling air as indicated by the arrows2?. This air flow 21 resists any tendency of fuel particles to enter thespace between shroud 24 and surface 20.

It has been found in much actual operation that this arrangement doeseffectively and completely prevent the deposition of carbon particleswhich might tend to plug the fluid discharge orfices. At the same time,this air flow also serves to cool the nozzle tip parts, so as topreserve them from deterioration due to exposure to the extremely hightemperature gases in the combustion space. The shroud of course acts asa radiation shield between the nozzle tip parts and the flame in thecombustion space. Tests of a gas turbine cornbustor in accordance withmy above-mentioned copending application and having an improved fuelnozzle in accordance with the present invention, show that thecombination is so efficient that there appears to be no upper limit ofblow-ou that is, the fuelair ratio may be increased apparently withoutlimit, without causing blow-out. This is in sharp contrast to experiencewith other types of fuel nozzles and combustors in which there is adefinite limit of fuel-air ratio beyond which blow-out occurs. Theconstant spray angle produced by nozzles incorporating the presentinvention is believed to be of the utmost importance in obtaining suchgreatly improved results.

While a preferred embodiment of the invention has been describedspecifically, it will be apparent that many similar structures may bedevised which will operate similarly, and I desire to cover by theappended claim all such changes and modifications as fall within thetrue spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

In a dual liquid spray nozzle of the vortex type, the combination ofwalls defining an outer whirl chamber and including a forward wallportion defining a circular discharge orifice, the outer chamber andorifice being constructed to produce a hollow conical spray pattern of apreselected cone angle, and walls defining a second smaller whirlchamber disposed coaxial within said outer chamber and having a conicalforward wall portion of reduced diameter adapted to be disposed withinthe air core formed by whirling liquid in the outer chamber in normaloperation, the inner chamber and orifice being constructed to produce ahollow conical spray pattern of the same preselected cone angle, saidforward wall portions defining together a central sharp-edged circularorifice communicating with the second whirl chamber and closelysurrounded by a sharp-edged annular orifice communicating with the outerwhirl chamber, said inner and outer orifices lying in the same planewhereby REFERENCES CITED The following references are of record in thefile of this patent:

UNITED STATES PATENTS Number Name Date 1,093,996 Kestner Apr. 21, 19141,526,429 Morse Feb. 17, 1925 1,536,046 Anthony May 5, 1925 1,641,581Egan Sept. 6, 1927 2,374,290 Johansson Apr. 24, 1945 2,411,181 AltorferNov. 19, 1946

